1. Field of the Invention
The present invention relates generally to paint spraying systems, and more particularly, but not by way of limitation, to an electrostatic spray gun for spraying a quick-drying paint mixture of a base paint and a catalyst.
2. Description of the Prior Art
Electrostatic paint spray guns are well known. The guns disclosed in the present application are constructed by modifying a prior art gun manufactured by Binks Manufacturing Company of Franklin Park, Illinois, known as its Model 80 or Model 80C electrostatic gun.
Such electrostatic spray guns are known to be usable in the assembly-line painting of articles. These guns have been utilized by the assignee of the present invention in connection with the assembly-line painting of components of marine engines. Until recently, such painting was accomplished with single-part, non-catalyzed paints. The painting system typically included a tank in which the paint was stored and agitated to keep it well mixed, a pump which took paint from the tank and circulated cold paint through a loop returning to the tank and a takeoff line which took paint from the circulating loop and directed it through a line heater to a series of pressure regulators adjacent the inlets of a plurality of spray guns.
The Binks Model 80 spray guns are actuated by applying air pressure to a piston which moves a valve member to open an orifice so that paint can then flow from the pressure regulator to the orifice and out onto the articles to be painted. The amount of paint directed through the gun when the gun is in its open position is controlled by adjusting the pressure regulator. Such systems perform perfectly well when utilizing conventional non-catalyzed paints.
More recently, however, environmental regulations have encouraged the use of quick-drying paints which reduce the amount of pollutants released to the atmosphere. These quick-drying paints comprise a paint mixture made up of a base paint and a catalyst. After the base paint and catalyst are mixed, the paint will polymerize or set up much more quickly than would the previously used conventional paints. When these quick-drying paint mixtures are utilized with a system like that just described, considerably difficulties are encountered with the paint mixture setting up and plugging various components of the system such as the regulators immediately upstream of each of the spray guns.
The prior art also includes systems for mixing these quick-drying paints. The base paint typically is stored in a mixing tank from which it is drawn and circulated through a cold paint loop by a pump. Cold base paint is taken off from the cold paint loop and directed to a proportioner. Simultaneously, catalyst is directed to the proportioner. The proportioner allows both base paint and catalyst to flow in a predetermined proportion to a mixer which mixes the base paint and catalyst to form the quick-drying paint mixture. Heaters may be located in the system upstream of the mixer.